1. Field of the Invention
This invention relates to high speed analog-to-digital converters for converting an analog input signal to a plurality of digital signals and, more particularly, to digital equalization of an analog-to-digital converter configuration which employs a plurality of time interleaved analog-to-digital converters.
2. Discussion
Analog-to-digital converters are used in a wide variety of applications for converting an analog signal to a plurality of digital signals. Implementation of high speed analog-to-digital conversion may require that several individual analog-to-digital converters be time interleaved in order to obtain the necessary speed. The resulting configuration is a plurality of analog-to-digital converters, each being coupled in parallel with one another and timed sequentially. Given N number of converters, the resulting conversion is about N times the speed of a single converter.
Generally, such analog-to-digital converter configurations result in a greater distortion of the digital signals than if a single high speed analog-to-digital converter is used. This distortion results from variations in the characteristics amongst the individual time interleaved analog-to-digital converters. Typically, Such variations include differences in gain, offset, timing, frequency/phase response, non-linearity and non-monotonicity. Even if the individual converters initially have identical characteristics, these characteristics generally change with temperature, time, radiation, and power supply variations, amongst other possible causes.
It is therefore desirable to obtain a time interleaved analog-to-digital converter configuration that provides a response which essentially is equivalent to an ideal single high speed converter. In particular, it is desirable to obtain a time interleaved analog-to-digital converter configuration that eliminates individual variations of converter characteristics found amongst the plurality of analog-to-digital converters.